diff --git a/src/classes/email.php b/src/classes/email.php
index 2949bea2..9bff5866 100644
--- a/src/classes/email.php
+++ b/src/classes/email.php
@@ -34,7 +34,7 @@ class Email
 
         $html = $this->mjml;
 
-        if (ENV_IS_DEV) {
+        if (defined('ENV_IS_DEV') && ENV_IS_DEV) {
             /**
              * Ignore SSL certificate errors
              */